Poly(cyclosiloxane) composition and synthesis

ABSTRACT

A poly(cyclosiloxane) is synthesized by oxidation with water in the presence of a Pt catalyst, followed immediately by polycondensation of the Si—OH groups to form Si—O—Si linkages. Thus, pentamethylcyclopentasiloxane can be polymerized into poly(pentamethycyclopentasiloxane).

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject application claims the benefit and priority of U.S. patentapplication Ser. No. 60/329,678, filed Oct. 16, 2001.

The invention disclosed in this application was at least partiallysupported by the National Science Foundation under Grant Nos. 99-88808and 00-80035. The U.S. Government may have certain rights to theinvention herein.

TECHNICAL FIELD

This invention relates generally to the synthesis of newpoly(cyclosiloxane) compositions and networks. More particularly, thepresent invention relates to the polymerization ofpentamethylcyclopentasiloxane.

BACKGROUND OF THE INVENTION

Many cyclic polysiloxanes, including pentamethylcyclopentasiloxane(sometimes referred to hereinafter as D₅H) have been commerciallyavailable for a number of years. At one time, these materials seemedpromising for use in medical applications. They are known to be usefulas crosslinkers in silicone coatings and encapsulating materials used inthe electronic industry, as well as for other electronic applications,such as composites and adhesives. Hence, synthetic methods therefor areknown in the art.

For example, Haines, et al, U.S. Pat. No. 5,395,956, discloses a processfor the synthesis of organohydrogensiloxanes, namely cyclicorganohyddrogensiloxanes. An hydrozylate intermediate is rearranged viaan acidic rearrangement catalyst, such as a sulfonateddivinylbenzenestyrene copolymer resin, to form a cyclicorganohydrogen-siloxane having the formula

where n=3 to 12. As noted in the patent, such polysiloxanes are known inthe art, but this process for its production provides minimal loss ofsiloxanes due to crosslinking of the siloxanes to high molecular weightbyproducts. Accordingly, cyclic polysiloxanes such aspentamethylcyclopentasiloxane are known, but the industry has yet toderive poly(cyclosiloxanes) therefrom.

However, crosslinking different derivatives of cyclic polysiloxanes isknown in the art. In particular, Loo, U.S. Pat. No. 5,334,688, disclosesa crosslinked polymer or crosslinkable prepolymer, which is thehydrosilation reaction product of a cyclic polysiloxane, anorganosilicon compound having at least two Si—H groups, and an optionalthird ingredient, an aromatic polyene having at least one carbon-carbondouble bond. In Loo, U.S. Pat. No. 5,373,077, the divisional of the '688patent, the aromatic polyene is a required ingredient. These crosslinkedpolymers, while technically polycyclosiloxanes, are limited tohydrosilation reactions between cyclic polysiloxanes having the formula

wherein R is a saturated, substituted or unsubstituted alkyl or alkoxygroup or a substituted or unsubstituted aryl or aryloxy group, R¹ is asubstituted or unsubstituted hydrocarbon group having at least onenonaromatic carbon-carbon double bond reactive via hydrosilation, and nis 3 or 4; and cyclic polysiloxanes having at least two Si—H groups.However, these compositions are prepared only by way of a hydrosilationreaction wherein a Si—H group reacts with a vinyl or allyl group toprovide the Si—O—Si linkages.

Similarly, other multiple component networks (MCNs) have also beenprepared. For example, commonly owned U.S. application Ser. No.09/833,774 discloses multicomponent networks comprising the reactionproduct of a plurality of multifunctional, allyl-terminated polyethyleneglycols linked to a plurality of multifunctional siloxanes having atleast two SiH moieties for each siloxane. These multiple componentnetworks (MCNs) as well as the more traditional interpenetrating polymernetworks (IPNs) should be distinguished from single component networksor polymerization products that are random aggregates of condensedcyclic siloxanes comprising a great variety of linearly and threedimensionally connected and crosslinked rings. An MCN is defined as asingle elastomeric network comprising at least two chemically differentcovalently-bonded sequences while an IPN consists of two or moreunlinked, independent networks

Thus, the need continues to exist for a single component polymer, i.e.,a homopolymer, comprising a single polymeric species—namely a particularcyclic polysiloxane, networked in three dimensions to form apoly(cyclosiloxane).

SUMMARY OF THE INVENTION

Broadlly, the present invention is directed towards the synthesis of asingle component, cyclic siloxane-based polymer network. Moreparticularly, a poly(cyclosiloxane) network composition, preferablypoly(pentamethylcyclopentasiloxane), is synthesized. It has been foundthat such network compositions, such aspoly(pentamethylcyclopentasiloxane), have an extremely low glasstransition temperature (Tg) and exhibit an unprecedented combination ofproperties. Poly(pentamethylcyclopentasiloxane) has been found to be astiff brittle solid, to be insoluble in common solvents, and to fail toexhibit a melting endotherm, yet has an extremely low Tg, and isthermally stable up to at least 700° C.

The advantages of the invention over the known art relating to polymericcompositions and networks, which shall become apparent from thespecification that follows, are accomplished by the invention ashereinafter described and claimed.

In general, the present invention may be achieved by apoly(cyclosiloxane) network composition comprising cyclosiloxanemoieties having the formula

wherein each R is the same or different for each cyclosiloxane moietyand is selected from the group consisting of a hydrogen, an alkyl group,an aryl group, and a cycloalkyl group, and wherein n is an integer from3 to 8; wherein each R² is either hydrogen or oxygen provided that whenR² is an oxygen it is bonded to another cyclosiloxane moiety; andwherein each cyclosiloxane moiety is bound to at least two othercyclosiloxane moieties via Si—O—Si functionalities.

Other aspects of the present invention may be achieved by providing apoly(cyclosiloxane) network composition comprising the polymerizationreaction product of a plurality of cyclosiloxane moieties having theformula

wherein each R is the same or different for each cyclosiloxane moietyand is selected from the group consisting of a hydrogen, an alkyl group,an aryl group, and a cycloalkyl group, wherein n is an integer from 3 to8 and wherein each cyclosiloxane moiety is bound after polymerization toat least two other cyclosiloxane moieties via Si—O—Si functionalities.

Still other aspects of the present invention may be achieved byproviding a process for the preparation of a poly(cyclosiloxane) networkcomposition comprising providing cyclosiloxane moieties having theformula

wherein each R is the same or different for each cyclosiloxane moietyand is selected from the group consisting of a hydrogen, an alkyl group,an aryl group, and a cycloalkyl group, and wherein n is an integer from3 to 8; oxidizing each cyclosiloxane moiety with water in the presenceof a Pt catalyst to form at least two Si—OH groups from the Si—H groupspresent on each ring and immediately thereafter condensing the cyclicrings such that the SiOH groups on each ring react to provide Si—O—Silinkages between the cyclosiloxane moieties to form apoly(cyclosiloxane) network composition.

It will be appreciated that, in a particular embodiment of the presentinvention, n equals 5 and R is a methyl group. In that instance, eachcyclosiloxane moiety is pentamethylcyclopentasiloxane and thepolymerization reaction product is poly(pentamethylcyclopentasiloxane),sometimes referred to hereinafter a PD₅.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative graph of the Raman spectra ofpentamethylcyclopentasiloxane (D₅H), poly(pentamethylcyclopentasiloxane)(PD₅), and methanol as a reference, with the spectra normalized to theintegrated intensity of the C—H vibrational modes.

FIGS. 2A, 2B, and 2C are representative graphs of the differentialscanning calorimetry (DSC) traces of D₅H, PD₅ (in the range of −200 to+50° C.) and PD₅ (in the range of 0 to 600° C.), respectively.

FIG. 3 is a representative graph of the Brillouin spectrum of PD₅ at−170° C. and 80° C.

FIGS. 4A and 4B are representative graphs comparing the temperaturevariation of ν₀ and Γ, respectively, of Brillouin peaks in D₅H, PDMS,and PD₅ (one prepared in solution, the other prepared in bulk).

DETAILED DESCRIPTION OF THE INVENTION

As disclosed hereinabove the present invention is directed toward thesynthesis of poly(cyclosiloxane) compositions and, more particularly,toward the polymerization of cyclic polysiloxanes having the formula

wherein each R is the same or different for each siloxane moiety and isselected from the group consisting of a hydrogen, a substituted orunsubsitituted alkyl group, a substituted or unsubstituted aryl group,and a substituted or substituted cycloalkyl group, and wherein n is aninteger from 3 to 8. Such a composition provides a biocompatible,single-ingredient network having extremely good thermal stability,resistance to harsh chemical environments and a uniquely low glasstransition temperature.

Preferably, the compositions formed are poly(methylcyclohydrosiloxanes).Thus the R in the formula II above is a methyl group. A preferred cyclicpolysiloxane is pentamethylcyclopentasiloxane. Other examples ofpreferred cyclic polysiloxanes include, by way of example,trimethylcyclotrisiloxane, tetramethycyclotetrasiloxane, andhexamethylcyclohexasiloxane.

It will be appreciated, however, that the cyclic polysiloxanes of thepresent invention can be substituted or unsubstituted. Thus, anyalkylcyclohydrosiloxane can be employed, including hydrocarbonsubstituted cyclopentasiloxanes. It is believed and anticipated that anycyclic or aryl hydrocarbon substituted or unsubstitutedcyclopolysiloxane can be polymerized as well by the synthesis providedbelow. Examples of aryl cyclosiloxanes include, for example,pentaphenylcyclopentasiloxane, or hydrocarbon substituted arylcyclopentasiloxane. Examples of cyclic deratives includetritolylcyclotrisiloxane, and pentatolylcyclopentasiloxanes. Cyclicalkyl substituted cyclosiloxane derivatives include, for example,tri(cyclohexyl)cyclotrisiloxane, or penta(cyclohexyl)cyclopentasiloxanes.

Polymerization of these cyclic polysiloxanes is conducted by oxidationof the SiH group on the cyclosiloxane moiety to form SiOH groups andfollowed immediately by condensation of the cyclic ring to form complexaggregates of cyclosiloxane moieties. More particularly, it is believedthat the Si—OH groups are condensed to Si—O—Si to form Si—O—Si linkagesbetween the cyclosiloxane rings.

Polymerization of these cyclic polysiloxanes by oxidation andpolycondensation is conducted in the presence of a platinum-containingcatalyst and water. Only a very small amount of water, whose molarconcentration is equal to or less than the molar concentration of theSi—H groups in the system, is necessary for the reaction to occur.

The reaction may be conducted with or without solvents. When solventsare employed, it may be any typical aromatic, solvent including, by wayof example, benzene, xylene, toluene, hexane, cyclohexane, heptane,cycloheptane, and the like. The most preferred solvent is toluene.

The catalyst may be any platinum-based catalyst system, including aKarstedt's system (a platinum divinyl complex in toluene or xylene, suchas is available from United Chemical Technologies); chloroplatinic acidin isopropanol, bis(acetonitrile)platinum dichloride, bis (benzonitrile)platinum dichloride, platinum on carbon, platinum dichloride,cyclooctadieneplatinum dichloride, dicyclopentadieneplatinum dichlorideand metallocene platinum systems. The platinum catalyst is present in anamount of 0.0005% to 0.10% by weight of platinum, based on the weight ofthe monomers, preferably 0.001% to 0.05%, and most preferably 0.005% to0.01%. Most preferred is the Karstedt catalyst, Pt₂{[(CH₂═CH)Me₂Si]₂O}₃.A tin-containing catalyst such as tin octanoate may also be used as acatalyst. Likewise, other metal-containing complexes, for example,titanium complexes, zirconium complexes and rhodium complexes, may beused as suitable catalysts.

Scheme I hereinbelow shows the chemical polymerization reaction wherethe monomer is pentamethylcyclopentasiloxane (D₅H). The resultantpoly(pentamethylcyclopentasiloxane) is shown in Scheme I as PD₅. It willbe appreciated that PD₅ shows only a representative microarchitecture ofthe polymer, and that the present invention should not be limited tothis one polymer, it being understood that the present invention, asenvisioned, includes other cyclic polysiloxanes of the same or similarmicrostructure as D₅H.

As shown in Scheme I, the polymerization starts by the interactionbetween D₅H and Pt/H₂O, a reaction in which the monomer is converted toan intermediate of cyclopentanesiloxane rings in which some of the SiHgroups have been converted to SiOH groups. Gaseous hydrogen is evolvedduring the production of this intermediate, which has not been isolated.As noted hereinbelow, according to Raman spectroscopy under theconditions employed, an average of three Si—H groups per D₅H ring havebeen converted to Si—O—Si crosslinks. This Pt catalyzed oxidation in thepresence of water (SiH+H₂O→SiOH+H₂) is believed to produce gaseous H₂that leads to an intense bubbling observed during the initial phases ofthe synthesis. This energetically strongly favored conversion is drivenby the formation of strong Si—O bonds from relatively weaker Si—Hlinkages and by the entropy gain of gaseous H₂ evolution. Thecyclosiloxane intermediate carrying an average of three Si—OH groupsimmediately starts to undergo polycondensations. Obviously, oxidation ofSi—H and polycondensation of SiOH proceed simultaneously, a theorysupported by the inability to isolate the cyclopentanesiloxaneintermediate, as discussed hereinbelow. The water used for the oxidationis recovered by condensation (2 Si—OH→Si—O—Si+H₂O). The final product isa random aggregate of condensed cyclosiloxanes comprising a greatvariety of linearly connected and crosslinked rings.

In order to demonstrate practice of the present invention, the followingexperiments were carried out. The following are illustrative of thenature of the present invention and should not necessarily be construedas limiting the scope of the invention. Other materials and processingsteps or conditions may be substituted as is known in the art for thosematerials, steps or conditions described herein, it being understoodthat the scope of the invention continues to reside in the invention ashereinafter claimed.

Initially, the synthesis of poly(pentamethylcyclopentasiloxane) (PD₅)was accomplished through the polymerization ofpentamethylcyclopentasiloxane (D₅H). Polymerization of this singlecomponent PD₅ network was undertaken in a one neck, round bottom flaskunder conventional conditions in air under laboratory hoods, without anyspecial equipment or precautions. In particular, 2 mL of D₅H, acolorless viscous liquid, and 2 mL of toluene (obtained from commercialsources) were placed in the 100 mL round bottom flask containing aTeflon coated magnetic stirring bar, and the charge was stirred in anoil bath at 100° C. Polymerization of the cyclic polysiloxane wasinduced by adding about 20 μL of a Karstedt's catalyst (Pt with1,3-divinyltetramethyldisiloxane in xylene solution) to the stirredcharge, followed a few seconds later by the introduction of a drop (˜0.3mL) of water.

Soon after the addition of these ingredients, the colorless liquidcharge started to bubble intensely. This is believed to have been causedby the evolution of hydrogen gas. Bubbling continued for about 1 hourafter which the intensity of bubbling diminished. The viscosity of thecharge gradually increased and, after a few hours, stirring becameimpossible. The highly viscous gel was placed in the hood over night (toremove most of the solvent) and subsequently dried in a vacuum oven atroom temperature for two days. This procedure yielded colorless faintlyopaque brittle flakes. In order to speed up or accelerate the reactionand reduce the processing temperature, the system could alternatively besonicated using, for example, an ultrasound bath.

In a second experiment, PD₅ was be synthesized from D₅H in the absenceof the solvent. Specifically, the solvent-free synthesis of PD₅ wasconducted wherein aliquots (typically 2 mL) of D₅H were stirred in around bottom flask at 100° C., and a Karstedt's catalyst (Pt) and, soonthereafter, a drop of water (about 0.3 mL) was again added. Bubblingstarted immediately again and was observed for about 30 to 60 minutes.Gradually, the bubbling subsided and stirring stopped because theviscosity of the system had increased substantially. A transparentcolorless brittle material was obtained that was dried in the hood and,subsequently, in the vacuum oven for two days at ambient temperatures.

Several tests were then performed on the resulting brittle, colorless,flaky powder material, some of which were used to characterize thepolymer. For instance, efforts were made to compression mold thematerial. Thus, the powdery samples of PD₅ were heated in a laboratory(Craver) press for about 10 minutes at 15 tons of pressure and at atemperature of about 300° C. There was no evidence of flow of any of thesamples which retained their brittle powder consistency.

The water uptake/absorption of the samples were also determined. Welldried PD₅ samples comprising a few large flakes of the sample driedunder vacuum for about one week at room temperature (about 23° C.) wereweighed, placed in water and heated to about 70° C. After one week ofsoaking, the flakes were filtered, thoroughly blotted with paper towelsand weighed again. The water uptake was calculated from the weightincrease with the average increase being about 3 weight percent. (SeeTable I).

Instrumental techniques were then used to characterize the polymer. Themelting point and glass transition temperature (Tg) of the PD₅ polymerwas determined by differential scanning calorimetry (DSC). This test wascarried out by a DuPont 2100 Thermal Analyzer under a nitrogenatmosphere. The samples were placed in aluminum containers and cooled toabout −200° C. DSC thermograms were obtained by heating the samples 10°C. per minute. Melting points were obtained as the minima of DSC scans,while the mid-point method gave glass transition temperature. Averagesof at least three trials are reported in Table I, while FIG. 2 showsrepresentative resultant scans.

TABLE I Selected Properties of PD₅ Visual appearance: Colorless, brittleflakes, powders Solubility: Insoluble in common organic solvents Wateruptake/absorption: 3% by weight Tg (° C.): −151 +/− 6° C. by DSC; −125+/− 20 by Brillouin scattering Permeability: Permeable to oxygen Thermaldecomposition (TGA): No significant weight loss up to 700° C.

Thermal Gravimetric Analysis (TGA) was obtained with a DuPont TAinstrument, Hi-Res TGA 2950. Samples for this test were heated undernitrogen from room temperature (about 23° C. to about 700° C. at a rateof about 10° C./minute. According to the results of TGA studies, the PD₅samples were extremely thermally stable, with no significant weight lossor decomposition up to at least about 700° C. in the nitrogenatmosphere.

Raman spectra were obtained by the use a Jobin Yvon T64000 triplemonochromator. Brillouin scattering spectra were obtained by atandem-interferometer (Sandercock model). Both, Raman and Brillouinspectra were obtained in back-scattering geometry with an Ar⁺⁺ laser asan excitation source, λ=514.5 nm, and 50 mW power on the samples. Theoverall chemical compositions were obtained by analysis of Ramanscattering spectra.

More particularly, structural analysis of PD₅ polymers was carried outby Raman scattering, which, like IR spectroscopy, provides molecularvibration information. Each chemical bond possesses a characteristicfrequency of vibrations and the concentration of specific chemical bondscan be determined by mode analysis. FIG. 1 shows the Raman spectra ofD₅H, PD₅ and methanol as a reference. The spectra are normalized to theintegrated intensity of C—H modes. The mode at about 2200 cm⁻¹corresponds to the vibration of the Si—H bond. The modes in the2750–3000 cm⁻¹ range correspond to different C—H vibrations, and thosein the 3200–3700 cm⁻¹ (see inset of FIG. 1) range correspond to O—Hvibrations.

As shown in FIG. 1, the C—H modes of D₅H and PD₅ PD₅ are essentiallyidentical, suggesting that the methyl groups did not get distorted inthe polymer. Assuming that the number of methyl groups did not changeduring the polymerization, the changes in the number of Si—H bonds canbe determined. The integrated intensity of the Si—H mode in PD₅ relativeto that in D₅H decreased to about 0.4±0.05, which indicates that anaverage of three out of the five Si—H bonds per D₅H ring havedisappeared during polymerization.

The Raman spectrum of PD₅ does not indicate changes in the O—H vibrationrange. By comparing the integrated intensities above 3200 cm⁻¹, it isestimated that the number O—H bonds is less than 0.02 per methyl group.Thus the number of O—H bonds in the polymer is negligible, if not zero,which indicates a substantial absence of dangling —OH end groups.

According to these results, an average of three out of five Si—OH bondsper D₅H ring has been converted to Si—O—Si bonds during thepolymerization. Rings may carry one to four Si—H groups; at present thenumber of Si—H functions per ring cannot be determined precisely.Importantly, however, the average functionality of the rings is threewhich gives rise to a three-dimensional network.

Based upon the results of the characterization of these polymers, itwill be appreciated that the sequence of events in the reaction and thepolymer microstructure itself are important for devising processingstrategies for the production of this polymer. For instance, mixing theD₅H monomer with the Pt catalyst and water at room temperature or below,and quickly pouring the system into molds can produce shaped objects ofPD₅. Polymerization can be accelerated by heating to 100° C. or above.Annealing by heat soaking may also help to increase the overallmolecular mass of the final product.

The process yields optically clear transparent stiff to brittlematerials. This method may be used to compression mold the PD₅ polymerof the present invention into any of a number of useful articles,including, for example, biocompatible membranes for use in conjunctionwith silicone rubber articles. It should be noted again that heating ofpowdery samples of PD₅ in a Craver laboratory press for 10 minutes at 15tons and 300° C. did produce not show evidence of flow and the samplesretained their brittle powdery consistency.

Interestingly, there is a dearth of information on the melting point(Tm) of D₅H in the scientific literature. The Gelest catalogue lists Tm,D₅H=−108° C. According to our DSC studies, the melting endotherm of D₅H,shown in FIG. 2, indicates Tm, D₅H=−137.6±1.0° C., which is an averageof five determinations.

The glass transition temperatures (Tg) of the monomer and polymer weretested to be Tg, D₅H=−152±2° C. and Tg, PD₅=−151±6° C., respectively.The average of four determinations for monomer and polymer is shown inFIG. 2. The repeatability of the heating and cooling cycles in scans Aand B were excellent and therefore only one trace is shown. For PD₅ inthe 0 to 600° C. range, reproducible traces were obtained after the6^(th) heating/cooling cycle. FIG. 2C shows heating scans 7–10. Theorigin of the transition at about 80° C. is obscure, as well as theascending portion of the scans above about 500° C.

The very low Tg of PD₅ is indeed surprising and unprecedented. A recentpublication by Nakamura, entitled “Which Polymer Has the Lowest Tg?”identifies polydiethylsiloxane (PDES) with the lowest Tg amongpolyorganosiloxanes. Sources cited therein variously fix Tg, PDES at−143° C. or −133° C. by DSC. In either case, these Tg values are indeedlower than that of PDMS (Tg, PDMS=−123° C.), commonly regarded as havingthe lowest Tg among polymers. According to repeated DSC determinations,the Tg of PD₅ is below that of even PDES by about 10° C.

While not wishing to be bound by any particular theory, it is believedthat the very low Tg of PDMS is most likely due to the large number ofrotational conformers of the two methyl groups per repeat unit in thechain, the rotation of which is relatively unhindered on account of thelarge free volume in PDMS. Accordingly, it is believed that the low Tgof D₅H is due also to the existence of the many conformers and rotamersin this molecule. The Tg of PD₅ is not much different from that of itsmonomer, which is not an unusual occurrence. Evidently, the increasednumber of conformers prevailing in PD₅ compensates for the loss oftranslational entropy due to the polymerization of D₅H.

Brillouin scattering provided elastic constants (sound velocity) andmechanical relaxation at GHz frequencies. The D₅H and PD₅ samples wereplaced in vacuum tight ampoules. PD₅ films were placed between twosapphire windows to ensure good thermal contact. PDMS as a referencematerial was also determined. Brillouin measurements were performed atdifferent temperatures with cooling and heating rates of 0.6° C./minute.Computer software was prepared to control the heating and cooling cyclesof the experiments. The data obtained by cooling agreed well with thoseobtained by heating, i.e., significant hysteresis was not observedduring the slow temperature changes used.

This technique analyzes the scattering of light by acoustic wavespropagating in a material. For a given scattering angle Θ, the frequencyof the Brillouin peak ν₀ is proportional to the sound velocity V in thematerial:

$v_{o} = {\frac{2\;{nV}}{\lambda}{Sin}\mspace{11mu}( \frac{\theta}{2} )}$where n is the refractive index whose variation with the temperature isusually negligible. The main variation of frequency ν₀ is related tochanges in the sound velocity which in turn is directly related to theelastic modulus K=V²/ρ, where ρ is the density of the material. Thespectra were fitted by using the standard expression for a dampedharmonic oscillator:

${I(v)} \propto \frac{\Gamma}{( {v^{2} - v_{0}^{2}} )^{2} + ( {2v\;\Gamma} )^{2}}$where Γ is the width of the Brillouin scattering which is proportionalto the damping of the sound wave at a given frequency.

FIG. 3 shows the Brillouin spectra of PD₅ at −170 and 80° C. TheBrillouin peaks have shifted by a frequency ±ν₀ from the laser linecentered at zero. A difference in the frequency ν₀ and width of thepeaks Γ can be clearly seen.

FIG. 4 presents the temperature variation of ν₀ and Γ for D₅H and twoPD₅ samples. The data for the two polymer samples, one prepared insolution, the other in bulk, are consistent within experimentalvariation. The data for PDMS are also shown for comparison. The Tgs canbe estimated from the changes in the slopes of temperature variations ofν₀ and Γ. For D₅H and PDMS the temperature strongly influences ν₀ and Γand the glass transitions can be clearly observed. Above the Tg, theelastic modulus decreases and the relaxation increases which leads to astrong decrease in ν₀ and a sharp increase in Γ. In contrast, for PD₅,both ν₀ and Γ show a gradual slow decrease over the entire temperaturerange and a distinct glass transition cannot be discerned. Such a broadrange of glass transitions is usually observed with covalently bondedso-called “strong” glass-forming systems. The term “strong” was coinedby C. A. Angell. It will be appreciated that as used herein, the term“strong” indicates that the system strongly resists temperature damages,i.e., the temperature has to be increased far above the Tg to reach thelow viscosity (liquid) state and short relaxation times. Silica glass isa traditional example for such strong glass-forming systems.

In FIG. 4B, PD₅ shows a strong shift of Γ toward high temperatures. Themaximum Γ appears when 2πτν₀=1, where τ is a characteristic relaxationtime that dampens acoustic modes. In polymers a maximum Γ usuallyappears at temperatures (T_(max)) not far above Tg. Indeed, according tothe data in FIG. 4B, T_(max) is approximately 1.45 Tg for PDMS, andT_(max) is about 1.6 Tg for D₅H. The maximum Γ for PD₅, however, appearsat a significantly higher temperature, T_(max) of about 2.6 Tg. Thesedata indicate a very slow change of relaxation time τ with temperature,a characteristic behavior of strong glass-forming systems.

Brillouin scattering has also been used to generate Tg information datafor the monomers and polymers of the present invention. For example, Tg,D₅H=−150±5° C. and Tg, PD₅=−125±20° C. The larger error for PD₅ is dueto extremely smooth transitions. The agreement between the Tg valuesobtained by DSC and Brillouin scattering is excellent for D₅H, and isconsidered within experimental error for PD₅.

Based upon the foregoing disclosure, it should now be apparent that theuse of the components described herein will carry out the objects setforth hereinabove. It is, therefore, to be understood that anyvariations evident fall within the scope of the claimed invention andthus, the selection of specific component elements can be determinedwithout departing from the spirit of the invention herein disclosed anddescribed. Thus, the scope of the invention shall include allmodifications and variations that may fall within the scope of thedescribed invention.

1. A poly(cyclosiloxane) network composition comprising: repeatingcyclosiloxane moieties having the formula

wherein each R is the same or different for each cyclosiloxane moietyand is selected from the group consisting of a hydrogen, an alkyl group,an aryl group, and a cycloalkyl group, and wherein n is an integer from3 to 8; wherein each R² is either hydrogen or oxygen provided that whenR² is an oxygen it is bonded to another cyclosiloxane moiety; andwherein each cyclosiloxane moiety is bound to at least three othercyclosiloxane moieties via Si—O—Si functionalities.
 2. Thepoly(cyclosiloxane) network composition according to claim 1, whereinR═CH₃.
 3. The poly(cyclosiloxane) network composition according to claim1, wherein n=5.
 4. The poly(cyclosiloxane) network composition accordingto claim 1, herein the glass transition temperature of thepoly(cyclosiloxane) network is −151±−6° C.
 5. A poly(cyclosiloxane)network composition comprising: the polymerization reaction product of aplurality of cyclosiloxane moieties having the formula

wherein each R is the same or different for each cyclosiloxane moietyand is selected from the group consisting of a hydrogen, an alkyl group,an aryl group, and a cycloalkyl group, wherein n is an integer from 3 to8 and wherein each cyclosiloxane moiety is bound after polymerization toat least two other cyclosiloxane moieties via Si—O—Si functionalities.6. The poly(cyclosiloxane) network composition according to claim 5,wherein n=5.
 7. The poly(cyclosiloxane) network composition according toclaim 5, wherein R=CH3.
 8. The poly(cyclosiloxane) network compositionaccording to claim 5, wherein each cyclosiloxane moiety is bound toexactly three other cyclosiloxane moieties.
 9. The poly(cyclosiloxane)network composition according to claim 5, wherein the glass transitiontemperature of the poly(cyclosiloxane) network is −151±−6° C.
 10. Aprocess for the preparation of a poly(cyclosiloxane) network compositioncomprising providing cyclosiloxane moieties having the formula

wherein each R is the same or different for each cyclosiloxane moietyand is selected from the group consisting of a hydrogen, an alkyl group,an aryl group, and a cycloalkyl group, and wherein n is an integer from3 to 8; oxidizing each cyclosiloxane moiety with water in the presenceof a Pt catalyst to form at least two Si—OH groups from the Si—H groupspresent on each ring and immediately thereafter condensing the cyclicrings such that the SIOH groups on each ring react to provide Si—O—Silinkages between the cyclosiloxane moieties to farm apoly(cyclosiloxane) network composition.
 11. The process according toclaim 10, wherein R=CH₃.
 12. The process according to claim 10, whereinn=5.
 13. The process according to claim 10, wherein no Si—OH functionalgroups remain.